In semiconductor manufacture, integrated circuits are formed on a wafer formed of silicon or another semiconducting material. In general, layers of various materials which are either semiconducting, conducting or insulating are utilized to form the integrated circuits. These materials are doped, deposited and etched using various well known processes. Each wafer is processed to include a large number of individual semiconductor dice or chips.
Following the wafer formation process, the wafer is diced to separate the individual dice for packaging or for use in an unpackaged form. The two main techniques for wafer dicing are scribing and sawing. With scribing, a diamond tipped scribe is moved across the surface of the wafer along pre-formed scribe lines. These scribe lines are also referred to as "streets". The diamond scribe forms shallow scratches in the wafer surface. Upon the application of pressure, such as with a roller, the wafer separates along the scribe line. The breaks in the wafer follows the crystal lattice structure of the wafer substrate. Scribing can be used for wafers that are about 10 mils or less in thickness. For thicker wafers, sawing is the preferred method for dicing.
With sawing, a diamond-tipped saw rotating at high rpms contacts and saws the wafer along the streets. Sawing can be partially or completely through the wafer. Typically with saw cutting, the wafer is mounted on a supporting member such as an elastomeric adhesive film stretched across a film frame.
One problem with either scribing or sawing is that chips and gouges can form along the severed edges of the die. In addition, cracks can form and propagate from the edges into the substrate of the die. Chipping and cracking are particularly a problem with scribing because only one side of a rectangular die can be scribed in the &lt;110&gt; direction. Consequently, cleaving of the other side of the die results in a jagged separation line. Because of chipping and cracking, additional spacing is required between the dice on the wafer to prevent damage to the microcircuits. As a result, not as many dice can be formed on a standard sized wafer and wafer real estate is wasted.
Another problem with conventional scribing and sawing processes is that the equipment is complicated and therefore expensive to install and maintain. Diamond tipped scribes and saw blades in particular are very expensive and require frequent replacement. In addition, with these processes the wafers must be scribed or sawed one at a time. Consequently, throughput is limited unless a large number of machines are employed.
To overcome some of the problems associated with scribing and sawing, abrasiveless methods for dicing semiconductor wafers have been proposed. For example, one proposed abrasiveless dicing mechanism can be etching with a wet etchant. However, such an abrasiveless method has not heretofore been successfully utilized for volume semiconductor manufacture. One problem with dicing a wafer using etching techniques is that wet etchants for silicon can adversely affect the exposed bond pads on the dice. Bond pads formed of aluminum are particularly susceptible to degradation by an etchant such as KOH. In addition, any residuals of the etchant on the die can be catastrophic to the die performance.
In view of the foregoing, it is an object of the present invention to provide an improved method and apparatus for dicing semiconductor wafers into singulated dice. It is yet another object of the present invention to provide an improved method and apparatus for dicing semiconductor wafers that is abrasiveless and that does not form cracks or chips in the singulated dice or adversely affect the electrical devices formed on the dice. It is a still further object of the present invention to provide an improved method of wafer dicing that does not require expensive equipment and consumable components and in which a high volume throughput can be achieved. Other objects, advantages and capabilities of the present invention will become more apparent as the description proceeds.